1. Field of the Invention
The present invention relates to a method of engine control and, more particularly, to a method and system for estimating engine cooling fan power losses.
2. Background Art
In the control of heavy duty internal combustion engines, conventional practices utilize electronic control units having volatile and non-volatile memory, input and output driver circuitry, and a processor that executes instructions to control the engine and its various systems and subsystems. The electronic control units communicate with numerous sensors, actuators, and other electronic control units to control various functions such as various aspects of field delivery, transmission control, and engine control. Typically, one of the electronic control units operates to control engine cooling fans in accordance with received fan request signals. Although many types of fans are used with internal combustion engines, the control schemes used to control the fans are simple and the control algorithms are conservative to reduce the possibility of overheating and engine component failure.
At the same time, the heavy duty engine business is extremely competitive. Greater demands are being placed on engine manufacturers to design and build engines that provide better engine performance, improved reliability, and greater durability while meeting more stringent emission and noise requirements. One of the greatest customer demands is to provide more fuel efficient engines. With increasing fuel costs, demands for fuel efficiency are becoming so great that all vehicle components and accessories are being scrutinized in attempts to reduce power consumption. The engine fan represents a significant load on an engine, reducing available power and torque when the fan is operating.
For the foregoing reasons, it would be desirable to have an improved method of estimating engine power losses due to the cooling fan and allowing for more aggressive fan control to improve vehicle fuel efficiency. Additionally, transmissions require more accurate information concerning actual power available to them at the engine flywheel (i.e., the power input to the transmission).